As a radiographic apparatus for use in medical diagnostic imaging or nondestructive inspection with radiation such as an X-ray, a radiation imaging apparatus in which pixels each formed by combining a switch such as a thin-film transistor (TFT) and a conversion element such as a photoelectric conversion element are arranged has been put into practical use. The switch is arranged between the conversion element and a column signal line, and the switch is put into a conductive state to read out a signal from the conversion element via the column signal line. In recent years, increasing functionality of the radiation imaging apparatus has been considered. As one function, including a function of monitoring radiation irradiation has been considered. This function enables detection of a timing at which the radiation irradiation from a radiation source is started, detection of a timing to stop the radiation irradiation, and detection of an irradiation amount or an integrated irradiation amount of the radiation, for example.
In Patent Literature 1, there is disclosed a radiation detector configured to detect an irradiation amount of radiation to detect a timing to stop radiation irradiation, and to acquire a radiation image. The radiation detector according to Patent Literature 1 includes a photoelectric conversion element, a line for reading out radiation image data, a line for reading out radiation irradiation amount data, a switch element, and a storage capacitor. The line for reading out the radiation image data is connected to the photoelectric conversion element via the switch element, and the storage capacitor is arranged between the line for reading out the radiation irradiation amount data and the photoelectric conversion element.
According to the structure described in Patent Literature 1, in a case where the irradiation amount of the radiation is detected, the radiation irradiation amount data is read out via the storage capacitor, with the result that an amount of charge generated by the radiation is stored, and the radiation image data is not attenuated. Therefore, also in a pixel for detecting a radiation irradiation amount, image data may be obtained without being attenuated.